title: Formation of oligomeric rings by XcpQ and PilQ, which are involved in protein transport across the outer membrane of Pseudomonas aeruginosa.
abstract: Pseudomonas aeruginosa is able to translocate proteins across both membranes of the cell envelope. Many of these proteins are transported via the type II secretion pathway and adopt their tertiary conformation in the periplasm, which implies the presence of a large transport channel in the outer membrane. The outer membrane protein, XcpQ, which is involved in transport of folded proteins across the outer membrane of P. aeruginosa, was purified as a highly stable homomultimer. Insertion and deletion mutagenesis of xcpQ revealed that the C-terminal part of XcpQ is sufficient for the formation of the multimer. However, linker insertions in the N-terminal part can disturb complex formation completely. Furthermore, complex formation is strictly correlated with lethality, caused by overexpression of xcpQ. Electron microscopic evaluation of the XcpQ multimers revealed large, ring-shaped structures with an apparent central cavity of 95 A. Purified PilQ, a homologue of XcpQ involved in the biogenesis of type IV pili, formed similar structures. However, the apparent cavity formed by PilQ was somewhat smaller, 53 A. The size of this cavity could allow for the transport of intact type IV pili.
authors.affiliation: Department of Molecular Cell Biology and Institute of Biomembranes, Utrecht University, The Netherlands. w.bitter@biol.ruu.nl
authors.forename: W
authors.initials: W
authors.lastname: Bitter
authors.forename: M
authors.initials: M
authors.lastname: Koster
authors.forename: M
authors.initials: M
authors.lastname: Latijnhouwers
authors.forename: H
authors.initials: H
authors.lastname: de Cock
authors.forename: J
authors.initials: J
authors.lastname: Tommassen
mesh_terms: D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000502:physiology; D001426:Bacterial Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000502:physiology; D001692:Biological Transport; D015153:Blotting, Western; D002352:Carrier Proteins / Q000737:chemistry* / Q000502:physiology; D004591:Electrophoresis, Polyacrylamide Gel; D036781:Fimbriae Proteins; D008565:Membrane Proteins; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009842:Oligopeptides / Q000502:physiology; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000378:metabolism*
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D008565:Membrane Proteins; D009842:Oligopeptides; C089841:XcpQ protein, Pseudomonas aeruginosa; C084295:pilQ protein, bacteria; D036781:Fimbriae Proteins